This document relates generally to electronic devices, and more specifically to methods of forming packaged electronics devices and structures.
Many electronic device applications mandate high levels of integration and functionality on the smallest possible platform. In certain applications, semiconductor devices are assembled in small outline leadless type protective packages. One common type of such protective package is the quad-flat pack no-lead type package or “QFN” package. In past QFN packages, the input/output (“I/O”) pads were placed surrounding and spaced apart from a flag portion or die attach portion where the semiconductor chip was placed. Wire bonds connected the semiconductor chip to the I/O pads. The I/O pads were placed in a single row configuration around the flag portion, or they were placed in a multi-row configuration around the flag portion. The multi-row I/O configurations were desired to support higher pin-count devices.
One previous QFN package with a multi-row I/O configuration used staggered or alternating I/O pads that were held together in a leadframe with tie bars until final assembly when the I/O pads were all separated into individual pads. In another previous multi-row I/O configuration, the outer rows of I/O pads were held together using a tie bar, and the inner row of I/O pads was tied to the flag until final assembly when the I/O pads and the flag were all separated into individual and isolated structures. In both previous configurations, the assembled package consisted of a separate and distinct flag portion that held the semiconductor chip, a separate and distinct inner row of I/O pads, and a separate and distinct outer row of I/O pads.
One problem with the previous QFN multi-row I/O configurations was that the overall package size had to be increased to make room for the multiple rows of I/O pads and the structures that held them in place (for example, tie bars) until final assembly. This limited the number of I/O pads that could be used, or required that the overall package size be increased, which is undesirable.
Accordingly, structures and methods of manufacture are needed for packages with multiple rows of I/O pads that support higher I/O densities in small outline electronic packages, such as QFN type packages.
For simplicity and clarity of illustration, elements in the figures are not necessarily drawn to scale, and the same reference numbers in different figures denote generally the same elements. Additionally, descriptions and details of well-known steps and elements may be omitted for simplicity of the description. Further, although the following Detailed Description uses a QFN style package to illustrate the present invention, this use is intended as an example only, and it is understood that the present invention applies to other package styles as well that require multiple rows of I/O pads.